Nosocomial Infections Due to Multidrug-Resistant Pseudomonas Aeruginosa: Epidemiology and Treatment Options

Marilee D. Obritsch, PharmD; Douglas N. Fish, PharmD, FCCM; Robert MacLaren, PharmD; Rose Jung, PharmD


Pharmacotherapy. 2005;25(10):1353-1364. 

In This Article

Frequency of Multidrug-Resistant Pseudomonas aeruginosa

The frequency of MDRPA infections is difficult to ascertain. Surveillance studies evaluating in vitro susceptibility of commonly used antibiotics against clinical isolates of P. aeruginosa provide estimations of the rate of MDRPA infections.[14,15,16,17,18,19,20,21] However, there are a few limitations to consider. First, most of these surveillance studies did not use molecular techniques to eliminate clonal spread; thus, results may be an overestimation in outbreak situations. Second, these studies do not distinguish clinical infection from colonization. Finally, studies lack standardization in definitions of multi drug resistance, which impedes direct comparisons of rates among studies. Because of these limitations, the trends in the isolation of MDRPA should be emphasized rather than actual rates reported. Studies meeting our definition of multi drug resistance reported increasing trends in MDRPA.

From 1997-1999, the SENTRY Antimicrobial Surveillance Program reported MDRPA rates of 8.2% in Latin America, 4.7% in Europe, 1.6% in Asia-Pacific, 1.2% in the United States, and 0.9% in Canada.[16] Among 1215 isolates of P. aeruginosa collected from 1999-2000 in Japan, 3% were found to be multidrug-resistant.[18] Two recent surveillance studies reported increases in MDRPA in the United States.[14,17] From 1998-2001, the Surveillance Network reported that multidrug resistance increased from 5.5% to 7.0% of P. aeruginosa isolates in patients not in an intensive care unit and from 7.4% to 9.1% in patients in an intensive care unit.[14] The Intensive Care Unit Surveillance Study reported a significant increase in MDRPA isolates from 4% in 1993 to 14% in 2002 (p<0.0001).[17]

Rates of MDRPA in individual institutions are even higher than those reported in large surveillance studies. In a university hospital in Brazil, 10.2% of P. aeruginosa isolates (48/472) were reported as MDRPA in 1992.[9] An institution in Greece indicated that 24.3% (25/103) of non-duplicate P. aeruginosa isolates from 1996-1997 were resistant to all antimicrobials tested.[15] Among resistant strains of P. aeruginosa isolated from 1994-1998 in a French hospital, 24% (8/34) were reported as MDRPA.[19] A university hospital in Italy reported a single case of MDRPA isolated in 1992; however, the rate increased significantly to 17% in 1999 (p=0.03).[8] In the United States, a tertiary care teaching hospital reported similar increases in rates of MDRPA despite different definitions used.[20] Among 2344 P. aeruginosa isolates, an increase in MDRPA (resistance to ceftazidime, ciprofloxacin, and aminoglycosides) from 0.9% in 1994 to 5.6% in 2002 was identified. The same study evaluated multidrug resistance (to imipenem, ceftazidime, and ciprofloxacin) in 1989 P. aeruginosa isolates and reported an increase from 0.6% in 1994 to 4.7% in 2002. Recently, another academic medical center in the United States reported an increase in MDRPA from 0% (0/18) in 1998 to 32% (13/41) in 2002 (p=0.0025).[21] Therefore, rates of resistance are increasing on a global scale, as well as within specific institutions. Institution-specific surveillance of susceptibility of P. aeruginosa isolates to antipseudomonal agents and determination of rates of multidrug resistance are essential in guiding therapy in individual patients.